Single cancer cell 'spells danger'8th December 2008
According to research in the United States, scientists may have misunderstood the capability of some cancers to spread and cause new tumours.
They are now finding that even a single cancerous cell may pose a danger to the body.
Often enough only one cell of skin cancer was needed in order for a new tumour to begin to grow.
The finding challenges a previously held supposition that only certain types of cancer cells could fuel the spread of the disease.
Sean Morrison of the Howard Hughes Medical Institute said that the underestimation of tumour-causing cells is a general problem in many cancers.
Morrison and a research team from the University of Michigan used specimens of melanoma in their study.
Melanoma is a cancer well known for its capability of spreading lethally from one location in the body to the next.
Usually the capability of one cell to "seed" new tumours is probed by injecting large amounts of the cell into mice.
Mice with disabled immune systems are chosen, and the number of emergent tumours are counted.
Previously, the small proportion of tumours relative to the number of mice injected led scientists to believe that not all cancer cells could trigger a new tumour.
The ability to seed new tumours was hence confined to a smaller number of "cancer stem cells."
But Morrison said this approach was flawed, as the potency of the cells used to seed new tumours was underestimated.
The mice tested had retained some immune strength in defence against human cancer cells.
When Morrison's team injected melanoma into mice with even less immunity to the disease, they found that 250,000 times as many of the cells formed tumours.
Even when only one cell of melanoma was used, roughly 25% of the mice formed tumours.
Morrison said that as far as is known, this is the first time anyone has been able to show that individual cells from human cancers can efficiently form tumours and therefore that simply identifying and targeting a small subset of them would not work.
His researchers think that the underestimation of tumour-causing cells is a general problem in many cancers, and is not specific to melanoma.
Morrison's team could find nothing to differentiate one cancer cell from another in terms of potency.
He said that scientists should improve their tests in order to determine whether or not the potency of the cancers they are using is equal.
While the existence of cancer stem cells is not disproved, Morrison and his researchers say this shows that the cells of some cancers, at least, are all equally dangerous.
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Title: Single cancer cell 'spells danger'
Author: Luisetta Mudie
Article Id: 9460
Date Added: 8th Dec 2008